spectre.console/src/Spectre.Console/Composition/Borders/SquareBorder.cs

using System;

namespace Spectre.Console.Composition
{
    /// <summary>
    /// Represents a square border.
    /// </summary>
    public sealed class SquareBorder : Border
    {
        /// <inheritdoc/>
        protected override string GetBoxPart(BorderPart part)
        {
            return part switch
            {
                BorderPart.HeaderTopLeft => "┌",
                BorderPart.HeaderTop => "─",
                BorderPart.HeaderTopSeparator => "┬",
                BorderPart.HeaderTopRight => "┐",
                BorderPart.HeaderLeft => "│",
                BorderPart.HeaderSeparator => "│",
                BorderPart.HeaderRight => "│",
                BorderPart.HeaderBottomLeft => "├",
                BorderPart.HeaderBottom => "─",
                BorderPart.HeaderBottomSeparator => "┼",
                BorderPart.HeaderBottomRight => "┤",
                BorderPart.CellLeft => "│",
                BorderPart.CellSeparator => "│",
                BorderPart.ColumnRight => "│",
                BorderPart.FooterBottomLeft => "└",
                BorderPart.FooterBottom => "─",
                BorderPart.FooterBottomSeparator => "┴",
                BorderPart.FooterBottomRight => "┘",
                _ => throw new InvalidOperationException("Unknown box part."),
            };
        }
    }
}